Connectivity. What a great word. I always think of the butterfly effect when I think of connectivity. Someone told me once that it is actually a real effect. It is a part of chaos theory which describes how a small change in one condition can effect a much larger change in a later condition. The butterfly is a metaphor I suppose. The idea being that the flapping of a butterfly’s wings somewhere in South America can change the course of a hurricane in the Atlantic. When I think of connectivity, I also think of six degrees of separation. You know that one: the idea that everyone is connected to everyone else in the world through six other people.

The Environmental Protection Agency (EPA) uses the word “connectivity” as part of the title of their report issued in January 2015, which provides the science supporting the Clean Water Rule.  The report is entitled: “Connectivity of Streams and Wetlands to Downstream Waters: A Review and Synthesis of the Scientific Evidence.” The purpose of the report is to use currently available science in determining the connection of upstream and adjacent waters such as tributaries and wetlands to downstream waters. If you have been reading this blog for awhile you know the EPA issued the Clean Water Rule in the summer of 2015 in order to clarify the definition of the “waters of the United States.” They did so because of several Supreme Court cases where the Court’s written opinion essentially told EPA to determine which upstream and adjacent waters have a “significant nexus” to the chemical, physical or biological integrity of downstream waters of the United States before regulating those upstream and adjacent waters under the Clean Water Act. “Significant nexus” is the court’s word and I guess it is fancy lawyer talk for connection. At least that’s how EPA decided to interpret the word.

EPA is a regulatory agency with a lot of scientists and a lot of lawyers. The scientists and lawyers got together and they decided that “significant nexus” means connection. So they came up with some basic science questions that needed to be answered: What are the physical, chemical, and biological connections to and effects on downstream waters of 1) upstream ephemeral, intermittent and perennial streams, 2) adjacent riparian or floodplain wetlands and open waters, and 3) non-flood plain wetland and open waters.

Ephemeral, intermittent and perennial streams are tributaries to downstream waters. Perennial streams flow most of the year and there is usually a good connection between local or regional aquifers to the stream which keeps them flowing. Intermittent streams are dry part of the year but may have variable flow along their length depending on connection to groundwater.  Ephemeral streams are dry most of the year and flow is dependent on short lived rainfall events or melting snow.  Adjacent riparian or floodplain wetlands are the wetlands we see along the banks and in the shallow water areas of rivers, lakes and streams and in the floodplains of those water bodies. Think of the mighty Mississippi and all those floodplain areas with swamps. Those occur not only at the large scale of a river but at the small scale of a stream. Non-flood plain wetlands are the more diffuse and often widespread type of wetlands. The ones I’m more familiar with are the prairie potholes that exist in the north central part of the country in places like North Dakota, Minnesota and Montana. This area of the country was heavily glaciated during the Ice Age. The big land glaciers covering these states pretty much ground down and flattened everything in their path. When the glaciers receded they left a gouged up terrain of small depressions that fill with water and have all sorts of little microecologies. In many areas the prairie potholes connect with the water table in the glacial alluvium also left behind by the glaciers.

The reason the Supreme Court and the EPA are interested in those physical, chemical and biological connections or their “significant nexus” is because the main objective of the Clean Water Act is to restore and maintain the chemical, physical, and biological integrity of the nation’s waters. So you can see it would be pretty hard to maintain and restore the nation’s waters if the upstream and adjacent waters connecting to them are going “all to heck.” It is kind of like the butterfly effect. How does the larval cycle of an invertebrate in an adjacent wetland affect the welfare of the downstream fish population?  And it’s kind of like the six degrees of separation too. How does the water in a downstream river make its way there through a whole set of hydrologic connections, like tributaries and shallow aquifer recharge.

So the determination of connection through chemical, physical and biological processes is what the scientists at EPA considered in determining what would be covered under the Clean Water Rule. The report is a compendium of science from the scientific literature, meaning peer reviewed journals in which scientists publish their findings. So EPA performed no new science to make their determinations. EPA only looked at the work of others and synthesized it in about a 500 page report which reads like a textbook. In fact you could probably use it as a textbook on hydrologic connectivity.

Textbooks do a lot of defining of terms. It’s sometimes like learning a whole new language. And EPA’s report does a lot of defining of terms as well. One of the chief terms they defined was the definition of connectivity. EPA defined it as “the degree to which components of a watershed are joined and interact by transport mechanisms that function across multiple spatial and temporal scales. Primary transport mechanisms are surface water and groundwater flows, transport and transformation of physical and chemical materials and movements of aquatic and semiaquatic organisms.” Well that is a mouthful. My interpretation of this definition is that EPA is going to consider the various waters in a watershed connected when waters serve to increase or reduce chemicals downstream, when they impact on the supply and other physical attributes of downstream waters, and if there are organisms like fish that use upstream and adjacent waters to spawn, feed, and all the other things organisms do.

Today’s post is the first in a series on EPA’ Connectivity of Streams and Wetlands to Downstream Waters. The next posts will cover how EPA uses their definition of connectivity in determining through the scientific literature what tributaries, what riparian and floodplain wetlands, and what non-riparian, non-floodplain wetlands are part of the Clean Water Rule.